Yusuf's Brothers offer taking One of Them instead of Binyamin as a Slave, Yusuf rejects the Offer
When it was decided that Benyamin was to be taken and kept with Yusuf according to the law they adhered by, Yusuf's brothers started requesting clemency and raising compassion in his heart for them,
(He said: "Allah forbid, that we should take anyone but him with whom we found our property..."), `according to the judgement that you gave for his punishment,
إِنَّـآ إِذًا لَّظَـلِمُونَ
(Indeed, we should be wrongdoers.), if we take an innocent man instead of the guilty man. '
Ma'arif al-Qur'an
Mufti Muhammad Shafi
In verse 78, it was said: قَالُوا يَا أَيُّهَا الْعَزِيزُ إِنَّ لَهُ أَبًا شَيْخًا كَبِيرًا فَخُذْ أَحَدَنَا مَكَانَهُ ۖ إِنَّا نَرَاكَ مِنَ الْمُحْسِنِين . It means when the brothers of Sayyidna Yusuf (علیہ السلام) realized that nothing seems to be working here and they have no option left but to leave Benyamin behind, they started flattering the ` Aziz of Misr. They told him that Benyamin's father was very old and weak (his separation will be unbearable for him). Therefore, they requested him that he should detain anyone from among them, in lieu of him. They also told him that they were making that request to him in the hope that he, as they feel, appears to be a very generous person - or, he has been gener-ous to them earlier too.
Tazkirul Quran
Maulana Wahiduddin KhanOn ayahs 76–78
Joseph did not want his younger brother to depart. When Benjamin’s packs were being readied, Joseph put his drinking cup in his younger brother’s packs. This was no malicious subterfuge on the part of Joseph, but was done out of great affection for his younger brother. Previously Joseph had done something similar when he put all the money which they had brought to buy grain in his brothers’ packs. The brothers only realized it when they opened their packs once they were back home. This time too, as a gesture of affection and love to his brother, he put his drinking cup in his younger brother’s pack. This was neither known to Benjamin nor to the courtiers. In the meantime, the weighing cup of the king had been misplaced and the courtiers suspected Joseph’s brothers of stealing it. When they opened their packs, they found Joseph’s drinking cup in Benjamin’s bag. This was not the cup they were looking for, but it was a similar one. The difference in these two cups can be understood by the two different words used for them in the Quran. The drinking cup belonging to Joseph is called siqayah, while the royal measuring bowl is called suwa‘ (verse 72). The cup which was recovered from Benjamin’s bag was a siqayah not a suwa‘, as a feminine pronoun, ‘ha’ (istakhrajaha) used for the cup here refers to the drinking cup of Joseph, and not to the lost measuring bowl of the king. This was not, therefore, a trick on the part of Joseph to prevent his brother from leaving, but in the words of Quran, it was an inspiration from God: ‘We devised a plan on behalf of Joseph’. In this instance, if the law of the king of Egypt had been observed, Benjamin would not have been given into the custody of Joseph but would instead have been beaten and the cost of the stolen item recovered from him, for that was the punishment regularly meted out to thieves. This incident did not come about by Joseph’s intention. It happened due to divine arrangement: God attributed it to Himself, ‘We devised a plan on behalf of Joseph’ (kazalika kidna li yusufa).